Circuit arrangement for telephone or signaling systems with tube senders



Feb. 25, 1930. w, SCHAFFER t 1,748,561

CIRCUIT ARRANGEMENT FOR TELEPHONE OR SIGNALING SYSTEMS WITH TUBE SENDERSFiled March 22, 1923 awuemto'c WALTER SCHAFFEK Patented Feb. 25, 1930UNITED "STATES PATENT OFFICE WALTER SCHAFFER, on ,BERLIN, GERMANASSIGNOR To GnsEL scH FTwFriR DRAH'rLosn TELEGRAPI-IIE M. B. H., or, BERIN, GERMANY, A CORPORATION or GERMANY CIRCUIT ARRANGEMENT FOR TELEPHONEOR SIGNALING SYSTEMS WITH TUBE i w SENDERS i Application filed March 22,1923, Serial No. 626,736,and in Germany April 13, 1922*.

The present invention relates to a circuit arrangement which may be usedfor transmitting signals or radiating speech by means of tube senders.The circuit arrangement is represented in the drawing.

The current source is connected to the terminals 1 and 2. The current issupplied through the choke coil 3to the oscillating tube 4 the anode ofwhich is in turn connected through the condenser 5 with the oscillatingcircuit 6. Current is supplied in the usual manner to the cathodethrough an input circuit, and the grid is connected to the circuit 6through the grid condenser 8. The cathode of the oscillating tube 4 isconnected with a condenser 9 which in turn is connected with the gridconductor through a choke coil 10 adapted to prevent the passage of highfre- 'quency currents. The condenser 9 is connected in parallel with themodulating tube 11 the grid of which is controlled through thetransformer 12 by means of a telephone transmitter 13 which is connectedin series with the talking current supply 14. If the grid of themodulating tube 11 is affected by a negative momentary potential, thenthe tube resistance will be infinitely high, the

grid of the oscillating tube 4 cannot discharge and the oscillatingcurrent in the circuit 6 must become zero. If the grid of the modulatingtube 11 is affected by a positive momentarypotential, then itsresistance will become very small, the grid of the oscillating 1 tube 4;will be discharged and the current in the oscillation circuit 6 will beraised 'to its highest value. This arrangement is 'of par ticularadvantage because the anode of the modulating tube 11 is connecteddirectly v with thefcathode of the oscillating tube 4' 40 whereby thelatter may be readily grounded. The heated cathode of-the modulatingtube 11 isprotected from high frequency currents by means of the chokecoil 10, and the condenser 9 provides a further protection against highfrequency currents for the tube 11. When a negative potential is appliedto v the grid of the modulating tube 11, and its resistance is thereforeinfinitely high'then, as above stated, the grid of the oscillating tube4 cannot be discharged and the circuit 6 -will cease to oscillate. .Inorder to prevent the complete cessation of the oscillations. andconsequent disturbances of the speech, it is advisable to connect inparallel with the condenser 9 an additional resistance 15 which is ofsuch degree that the oscillations in thecircuit 6 will not cease whenthe resistance of the modulating tube 11 is infinitely high.

I generated in the well knownmanner which is thenconducted to the gridof the operating sender proper (amplifier) The above described effectofthe grid discharge may then be applied either to the tube of thecontrolling sender or conducted between the grid and the cathode of'theoperating tube proper amplifying tube). Obviously the grid conductor ofthe operating tube (amplifying tube) which leads to the coupling, maybe, protected against direct current by inserting a condenser. It isimmaterial in what manner the grid coupling is accomplished in the caseof amplifying or oscillation generating tubes, whether it isaccomplished by galvanic, inductive or capacitive means or by means of agrid circuit connection.

Having described my invention, what I claim is 1. In combination a firstelectron discharge minal connected to the cathode and'the capacityhaving a terminal connected to the control electrode, a'secondll'lClLlCtflllCHCOllnected between the cathode and anode electrodes andcoupled to the first inductance for generation of oscillations, a secondelectron.

tube having an anode and a cathode connected in parallel with saidseries connected inductance and capacity, means for varying theconductivity of said second tube for controlling the potential ofthecontrol electrode of said first tube and means between said firstmentioned control electrode and said second electron tube for protectingsaid second electron tube from high frequency oscillations generated bysaid discharge tube.

2. A high frequency transmitting device comprising an electron dischargetube having a cathode, an anode and a control electrode, a controllingcircuit for said control electrode comprising two parallel branches oneof said branches comprising a thermionic tube acting as a variableresistance and the other of said branches comprising a condenser and aresistance in parallel, and means in said controlling circuit and commonto both of said branches for protecting said thermionic tube from highfrequency oscillations generated by said discharge tube.

3. In a transmitting device, an electron discharge tube having cathode,anode and control electrodes, an inductance and a condenser connected inseries between the cathode and control electrodes the inductance havinga terminal connected to the cathode and the capacity having a terminalconnected to the control electrode, a resistance circuit in parallelwith said inductance and capacity for controlling said control electrodecomprising a fixed resistance and a variable resistance in parallel,means for varying said variable resistance in accordance with signals tobe transmitted and means controlled by said fixed resistance whereby amaximum value of said resistance circuit may be predetermined.

WALTER SCHAFFER.

